JP7484505B2 - Developing device and image forming apparatus - Google Patents

Description

The present invention relates to a developing device and an image forming device.

In electrophotographic image forming devices equipped with a developing device that uses a two-component development method, the developing device may be shipped from the factory filled with developer in order to reduce the use of packaging materials and cushioning materials. In such cases, a structure that enhances the sealing performance of the developing device is adopted to prevent developer leakage due to shocks such as tipping or falling during transportation of the device.

In such a highly airtight developing device, the pressure inside the developing device rises, and the toner supplied from the toner supply device into the developing device is trapped in the space above the developer surface due to air pressure, resulting in an unstable toner supply. As a method of mitigating the pressure rise inside the developing device, a technology has been proposed in which a pressure reduction hole with a filter is provided at the top of the housing of the developing device to suppress developer leakage and pressure rise.

However, the above-mentioned technology has a problem that when the developing device is shipped from the factory with developer filled, toner leaks through the filter provided on the upper part of the housing and soils the inside of the image forming device. Therefore, a technology has been proposed in which a flexible sheet is provided near the circumferential surface of a magnetic roller that is provided near the developing roller and transfers developer to the developing roller, in a manner that touches or is close to the developer carried on the circumferential surface of the magnetic roller (for example, see "Patent Document 1").

In the above-mentioned technology, the amount of developer in contact with the flexible sheet usually changes due to the variation in the gap of the developer regulating member in the initial state, the aging condition, or the environmental condition, and it is not easy to control the gap between the flexible sheet and the rotating body. Therefore, even if the leakage of toner from inside the developing device can be prevented, the pressure inside the developing device becomes very high, so that the filter installed on the upper part of the housing for suppressing the internal pressure is quickly contaminated, and the filter deteriorates early due to the rise in internal pressure, resulting in an increase in the amount of toner leaking from inside the device.
SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a developing device which solves the above-mentioned problems and is capable of suppressing a pressure rise inside the developing device and preventing toner from leaking from inside the developing device.

The invention described in claim 1 comprises a developer accommodating section that accommodates a two-component developer having a toner and a carrier; a developer carrier that rotates while carrying the two-component developer on its peripheral surface and supplies the toner in the two -component developer carried on its peripheral surface to another member at a supply position; a flexible member having one end supported at a predetermined position of the developer accommodating section that is downstream of the supply position in the rotation direction of the developer carrier, and having a contact portion that contacts the two-component developer carried on its peripheral surface and faces the developer carrier with a gap therebetween, and the other end being a free end ; and an opening provided in the developer accommodating section at a position facing the developer carrier , communicating the inside and outside of the developer accommodating section, and having a filter member , the opening being provided on an extension of a straight line connecting the center of rotation of the developer carrier and the contact portion .

According to the present invention, when the internal pressure in the developer storage compartment rises, an airflow is generated that flows from the inside to the outside of the developer storage compartment through the filter member, suppressing the rise in internal pressure in the developer storage compartment. This makes it possible to provide a developing device that can prevent toner from blowing out or leaking from the developer storage compartment and ensure a stable supply of toner.

1 is a schematic configuration diagram of an image forming apparatus to which an embodiment of the present invention can be applied; FIG. 2 is a schematic configuration diagram of a developing device according to an embodiment of the present invention. FIG. 2 is an enlarged schematic configuration diagram of a main part of a developing device according to an embodiment of the present invention. FIG. 2 is a schematic plan view of a main portion of a developing device according to an embodiment of the present invention.

1 shows a color copier as an image forming apparatus according to one embodiment of the present invention. Process cartridges 3Y, 3C, 3M, and 3K for forming toner images of the respective colors of yellow (Y), cyan (C), magenta (M), and black (K) are arranged in the center of a device main body 2 of the color copier 1. Each process cartridge 3 is provided with a corresponding photosensitive drum 4Y, 4C, 4M, or 4K as an image carrier.
1, a charging device, developing devices 5Y, 5C, 5M, and 5K, and photoconductor cleaning devices 6Y, 6C, 6M, and 6K (not shown) are disposed around each photoconductor drum 4 that rotates counterclockwise. An optical unit 7 that irradiates each photoconductor drum 4 with laser light is disposed below each process cartridge 3.

Above each process cartridge 3, an intermediate transfer unit 9 is provided, which has an intermediate transfer belt 8 onto which a toner image formed by each process cartridge 3 is transferred. The intermediate transfer unit 9 has a number of rollers that support the intermediate transfer belt 8, and the intermediate transfer belt 8 is driven to run in a clockwise direction in FIG. 1 by driving any one of the rollers to rotate. Primary transfer rollers 10Y, 10C, 10M, and 10K are provided on the inner periphery of the intermediate transfer belt 8, facing each photosensitive drum 4, for primarily transferring the toner image formed on each photosensitive drum 4 onto the intermediate transfer belt 8.

Downstream of the primary transfer roller 10K in the running direction of the intermediate transfer belt 8, there is provided a secondary transfer roller 11 that performs a secondary transfer of the toner image that has been primarily transferred onto the intermediate transfer belt 8 onto the transfer sheet S. Furthermore, upstream of the primary transfer roller 10Y in the running direction of the intermediate transfer belt 8, there is provided a belt cleaning device 12 that removes residual toner remaining on the intermediate transfer belt 8 after image transfer. Above the secondary transfer roller 11, there is provided a fixing device 13 having a heating roller and a pressure roller that fixes the toner image that has been secondarily transferred onto the transfer sheet S.

A paper feed unit 14 is disposed at the bottom of the device main body 2. The paper feed unit 14 has a paper feed cassette 15, a paper feed roller 16, and a pair of registration rollers 17, and the transfer sheet S stored in the paper feed cassette 15 is fed by the paper feed roller 16 toward the pair of registration rollers 17. The pair of registration rollers 17 feeds the transfer sheet S toward a secondary transfer nip portion where the secondary transfer roller 11 and the intermediate transfer belt 8 come into contact with each other at a predetermined timing when the toner image formed on the intermediate transfer belt 8 matches a predetermined position on the transfer sheet S.
At the top of the device main body 2, there are arranged toner bottles 18Y, 18C, 18M, and 18K, each containing toner of a corresponding color to be supplied to each developing device 5, a pair of discharge rollers 19 that discharges the transfer sheet S on which the toner image has been fixed by the fixing device 13 to the outside of the device main body 2, and a paper output tray 20 on which the discharged transfer sheet S is stacked.

Here, the operation of the color copying machine 1 when obtaining a color image will be briefly described.
First, each photoconductor drum 4 is uniformly charged by each charging device. After that, the optical unit 7 is operated to expose and scan the surface of the photoconductor drum 4 with laser light, and an electrostatic latent image based on image information is formed on the surface of the photoconductor drum 4. The formed electrostatic latent image is developed with toner of each color by the operation of each developing device 5, and a toner image of each color is formed on the surface of each photoconductor drum 4. The toner images on each photoconductor drum 4 are superimposed and transferred onto the intermediate transfer belt 8 by the operation of the corresponding primary transfer roller 10, and the surface of each photoconductor drum 4 to which the toner image has been transferred is cleaned by the photoconductor cleaning device 6 in preparation for the next image formation.

Meanwhile, in the paper feed section 14, the transfer sheets S in the paper feed cassette 15 are separated and fed one by one by the operation of the paper feed roller 16, and the fed transfer sheets S are sent to the secondary transfer nip section at a predetermined timing by the operation of the registration roller pair 17. The transfer sheet S, to which the full-color toner image formed on the intermediate transfer belt 8 is transferred in the secondary transfer nip section, is sent to the fixing device 13, where the transferred image is fixed, and then discharged onto the paper discharge tray 20 by the discharge roller pair 19. As with the photosensitive drum 4, the residual toner remaining on the intermediate transfer belt 8 is cleaned by the belt cleaning device 12. A predetermined amount of each color toner contained in each toner bottle 18 is replenished to the corresponding developing device 5 via the toner transport path by a toner replenishing device (not shown) as necessary.

Next, the developing device 5 will be described with reference to Figures 2 and 3. The developing device 5 is a developing device that uses a two-component developer consisting of toner and carrier, and has a developing roller 22, which is a developer carrier, and a doctor blade 23, which is a doctor member, inside a developing case 21, which is a developer storage section. The developing roller 22 is disposed opposite the photosensitive drum 4, which is another member to which the developer is transferred from the developing roller 22, and has a magnet roller provided inside and a developing sleeve provided around it. The doctor blade 23 regulates the amount of developer carried on the developing sleeve, making the amount of developer carried on the developing sleeve uniform.

The developing sleeve, which is made of aluminum and has a cylindrical shape, is disposed at a position that maintains a predetermined development gap with the photosensitive drum 4, and is driven to rotate in a clockwise direction in Fig. 2 by a driving means (not shown). The developing sleeve may be made of aluminum, or may be made of a non-magnetic material such as brass, stainless steel, or conductive resin.
A magnet roller is fixedly provided inside the developing sleeve to generate a magnetic field so that ears of developer are generated on the developing sleeve. The carrier constituting the two-component developer forms ears on the developing sleeve along the magnetic field lines generated by the magnet roller. Furthermore, charged toner adheres to the carrier that has formed the ears, forming a magnetic brush.

The magnet roller has a P1 pole (main pole) that is set so that the peak of the magnetic force faces the center of the photosensitive drum 4, and magnetic poles P2, P3, P4, and P5 are arranged in the order of the rotation direction of the developing sleeve from the P1 pole. A thin layer of developer formed on the developing sleeve by the P1 pole is formed in contact with the photosensitive drum 4, and toner is supplied for development from the developer layer located in the development area as the supply position C, which is the position facing the photosensitive drum 4.
Thereafter, as the developing sleeve rotates, the developer is moved back into the developing case 21 by the magnetic force from the P2 pole, and then the developer is peeled off the developing sleeve by the repulsive magnetic force of the P3 and P4 poles and falls into the developing case 21.

A first agitating screw 24 serving as a supply member is rotatably provided in the developing case 21 so as to be parallel to the developing roller 22. The first agitating screw 24 constantly supplies developer to the developing roller 22 by rotating in a clockwise direction in FIG. 2, and also transports the developed developer peeled off from the developing roller 22 in a first space 25 in the developing case 21 in its axial direction, while agitating and mixing the developer with new developer in the first space 25.
A second space 27 is formed in the developing case 21, which is partitioned by the first space 25 and the inner wall 26, and receives toner from a toner supply port (not shown). A second agitating screw 28 is disposed in the second space 27. The second agitating screw 28 rotates counterclockwise in Fig. 2 to agitate the toner and carrier supplied from the toner supply port (not shown), and conveys the developer while applying a predetermined charge potential to the toner. A toner concentration detection sensor 31 is provided below the second agitating screw 28, and is used to detect the toner concentration in the second space 27 and control the operation of a toner supply device (not shown).
The inner wall 26 is provided with communication ports 32, 33 (see FIG. 4) that communicate with the spaces 25, 27, and the developer circulates through the spaces 25, 27 via the communication ports 32, 33. Then, new developer is carried and transported by the P5 pole, and is formed into a thin layer on the developing roller 22 by the doctor blade 23, and the above-mentioned process is repeated.

As described above, a thin layer of developer is supplied onto the peripheral surface of the developing roller 22, and as the developing roller 22 and the first agitating screw 24 rotate, air current A shown in Figures 2 and 3 is generated within the developing device 5, i.e., within the developing case 21. This air current A is generated strongly as the developer on the developing roller 22 rubs against the developing case 21, and the action of this air current A causes the first agitating screw 24 to suck in the toner suspended within the developing case 21, enabling good developer supply.
However, as described above, developer is supplied onto the peripheral surface of the developing roller 22, and the supply amount of this developer is not always constant, so that a gap is generated between the developer and the developing case 21, weakening the strength of the airflow A, and there is a problem that the floating toner cannot be sufficiently sucked in. This is due to the initial variation in the amount of regulation by the doctor blade 23 and the fact that the fluidity of the developer changes over time, which deteriorates the surface properties of the developing roller 22 and reduces the amount of developer regulation. It is possible to set the gap between the developer on the developing roller 22 and the developing case 21 narrow in advance, but conversely, if the amount of developer regulation is too large, the developer will overflow.

In order to solve the above-mentioned problems, a urethane sheet 29 is provided as a flexible member inside the developing case 21. The urethane sheet 29 is provided so as to have a width equal to or greater than the longitudinal width (axial length) of the developing roller 22, in other words, across the entire longitudinal width of the developing roller 22, as shown in FIG. 4, and its base end 29a is fixed to the developing case 21 located downstream of the supply position C in the rotation direction of the developing roller 22 as shown in FIG. 3. The urethane sheet 29 is supported by the developing case 21 in such a manner that a contact portion 29b, which is a part of the urethane sheet 29, is constantly in contact with the developer on the developing roller 22, and the free end 29c extends toward the downstream side of the rotation direction of the developing roller 22 beyond the contact portion 29b. With this configuration, the urethane sheet 29 is disposed between the developing roller 22 and the developing case 21 facing the developing roller 22.
Due to the action of this urethane sheet 29, the developer on the developing roller 22 is always rubbed by the urethane sheet 29 regardless of the amount of developer carried, so that the air flow A can be constantly generated stably and floating toner can be sufficiently sucked in without causing the developer to overflow.

However, when the airflow A is strengthened by providing the above-mentioned urethane sheet 29, the internal pressure within the developing case 21 becomes extremely high, which may induce unexpected toner blowout or leakage, or excessive toner may be sent to a filter (not shown) provided at the top of the developing case 21, causing the filter to become soiled early and worsening toner scattering.
In order to solve such problems, in the present invention, the developer case 21 is provided with an opening 21a that communicates between the inside and outside of the developer case 21, and a filter member 30 is provided inside this opening 21a. The filter member 30 is disposed in a position that faces the contact portion 29b on the wall of the developer case 21, that is, at a position where the straight line D that connects the axis O of the developer roller 22 and the contact portion 29b passes through approximately the center of the length in the rotational direction of the developer roller 22, which is the longitudinal direction of the filter member 30 in FIG.
With this configuration, when air flow A becomes stronger and the internal pressure inside the developing case 21 rises, air flow B is generated flowing from the inside to the outside of the developing case 21 through the filter member 30, suppressing the rise in internal pressure inside the developing case 21. This makes it possible to prevent toner from blowing out or leaking from inside the developing case 21, and to provide a developing device that can provide a stable supply of toner.

In addition, in the above-mentioned configuration, the lower end of the filter member 30 in FIG. 3 is disposed upstream of the free end 29c of the urethane sheet 29 in the rotation direction of the developing roller 22. In other words, the downstream end of the opening 21a in the rotation direction of the developing roller is disposed upstream of the free end 29c of the urethane sheet 29 in the rotation direction of the developing roller. Therefore, the opening 21a is positioned so as to be completely covered by the urethane sheet 29, and the urethane sheet 29 prevents floating developer from adhering to the filter member 30, thereby preventing the filter member 30 from being soiled and maintaining the breathability of the filter member 30 for a long period of time.

Furthermore, in the above-mentioned configuration, the rotation direction of the first agitating screw 24 is the same as the rotation direction of the developing roller 22. This prevents the airflow generated in the developing case 21 by the rotation of the first agitating screw 24 from affecting the filter member 30, and prevents the filter member 30 from becoming soiled, so that the function of the filter member 30 can be maintained for an even longer period of time.

In the above embodiment and each modified example, a full-color copying machine 1 is used as the image forming device, but the image forming device is not limited to this, and the present invention can also be applied to printers, facsimiles, multifunction machines, and monochrome machines of these. In addition, in each embodiment, a configuration is shown in which a transfer sheet S is used as the recording medium on which an image is formed, but the transfer sheet S also includes cardboard, postcards, envelopes, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, overhead projector sheets, overhead projector films, resin films, etc., and any sheet-like material may be used as long as it is capable of forming an image.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the spirit of the present invention described in the claims, unless otherwise specifically limited in the above description.
The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

1. Image forming device (color copier)
4. Other members (photoconductor drum)
5 Developing device 21 Developer container (developing case)
21a Opening 22 Developer carrier (developing roller)
24 Supply member (first stirring screw)
29 Flexible member (urethane sheet)
29a Base end 29b Contact portion 29c Free end 30 Filter member C Supply position

JP 2011-47967 A

Claims (5)

a developer storage section that stores a two-component developer having a toner and a carrier;
a developer carrier that rotates while carrying the two-component developer on its circumferential surface and supplies the toner in the two-component developer carried on its circumferential surface to another member at a supply position;
a flexible member , one end of which is supported at a predetermined position of the developer accommodating section downstream of the supply position in the rotation direction of the developer carrier, the flexible member having a contact portion which contacts the two-component developer carried on the circumferential surface and faces the developer carrier with a gap therebetween, and the other end of which is a free end portion ;
an opening provided in the developer accommodating portion at a position facing the developer carrier , communicating an inside and an outside of the developer accommodating portion and having a filter member ;
The opening is provided on an extension of a straight line connecting the center of rotation of the developer carrier and the contact portion . 2. The developing device according to claim 1,
2. The developing device according to claim 1, wherein the flexible member is provided across the entire width of the developer carrier in the longitudinal direction. 3. The developing device according to claim 1,
the developing device having an opening whose entire area is disposed upstream of the free end in the direction of rotation; 4. The developing device according to claim 1,
A developing device comprising a rotatable supply member that supplies the two-component developer in the developer accommodating section to the developer carrier, the supply member rotating in the same direction as the developer carrier rotating in the same direction. An image forming apparatus comprising the developing device according to any one of claims 1 to 4.

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